PuTTY 0.56

What's new in this version:

- Security fix: a vulnerability discovered by iDEFENSE, potentially allowing arbitrary code execution on the client by a malicious SSH-2 server before host key verification, has been fixed. See vuln-ssh2-debug.
- Ability to restart a session within an inactive window, via a new menu option.
- Minimal support for not running a shell or command at all in SSH protocol 2 (equivalent to OpenSSH's "-N" option). PuTTY/Plink still provide a normal window for interaction, and have to be explicitly killed.
- Transparent support for CHAP cryptographic authentication in the SOCKS 5 proxy protocol. (Not in PuTTYtel.)
- More diagnostics in the Event Log, particularly of SSH port forwarding.
- Ability to request setting of environment variables in SSH (protocol 2 only). (However, we don't know of any servers that support this.)
- Ability to send POSIX signals in SSH (protocol 2 only) via the "Special Commands" menu. (Again, we don't know of any servers supporting this.)
- Bug fix: The PuTTY tools now more consistently support usernames containing "@" signs.
- Support for the Polish character set "Mazovia".
- When logging is enabled, the log file is flushed more frequently, so that its contents can be viewed before it is closed.
- More flexibility in SSH packet logging: known passwords and session data can be omitted from the log file. Passwords are omitted by default. (This option isn't perfect for removing sensitive details; you should still review log files before letting them out of your sight.)
- Unix-specific changes:
   + Ability to set environment variables in pterm.
   + PuTTY and pterm attempt to use a UTF-8 line character set by default if this is indicated by the locale; however, this can be overridden.